Based on work completed in the current grant period we propose the following hypothesis: The fatty streak is an inflammatory response to oxidized lipids in the artery wall at sites of predilection. We will continue to test this hypothesis in the next grant period and attempt to further delineate the mechanisms by which oxidized lipids can evoke such an inflammatory response. During the current grant period we (and others) have observed that animals with identical plasma lipoprotein levels and patterns can have dramatically different susceptibility to fatty streak formation. Our preliminary data suggest that such differences in susceptibility are genetically determined and in part may be due to antioxidant and detoxifying systems for oxidized lipids. We also have accumulated exciting preliminary data in this grant period that suggest that a new class of anti-inflammatory agents may have a role in preventing fatty streak formation. An important event in the development of more advanced atherosclerotic lesions is calcification of the lesion. We have preliminary evidence to suggest that cells of smooth muscle lineage may be responsible for arterial calcification. We will characterize these cells and determine the mechanism by which arteries calcify. We have accumulated evidence that the isoprenoid biosynthetic pathway is important in the development of fatty streaks both indirectly by influencing lipoprotein levels and perhaps directly by modifying cellular responses to oxidation. In addition, we have preliminary data to suggest that 7-alpha hydroxylase may play an important role in the development of fatty streaks under some conditions and that this too may be genetically determined. In addressing these questions we will use a combination of in vitro and in vivo approaches. We propose seven projects and three cores in this renewal application. To some extent all seven projects will study the molecular mechanisms that lead to fatty streak formation. However, Project 4 will focus on identifying the cells and determining the mechanism(s) of arterial calcification. Similarly, Project 6 will contribute to the overall goal of understanding fatty streak formation but will in addition continue to delineate the molecular mechanisms that regulate isoprenoid biosynthesis. Project 7 will explore the contributing role of 7-alpha hydroxylase to fatty streak formation and will also utilize quantitative trait loci mapping to determine the involvement of multiple genes in the development of the fatty streak. As a consequence of the diverse scientific backgrounds of the Faculty who are serving as Project Leaders we constitute a unique Program Project that has and will continue to bring an integrated approach to the problem of atherosclerosis utilizing biochemical, cell biology, genetic, molecular biology, and state-of-the- art ultrastructural strategies.